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A Field Comparison of Sampling Protocols for Measuring Lead in Drinking Water
Citation:
Porter, A., M. Deltoral, AND M. Schock. A Field Comparison of Sampling Protocols for Measuring Lead in Drinking Water. In Proceedings, Water Quality Technology Conference, Long Beach, CA, November 03 - 07, 2013. American Water Works Association, Denver, CO, ,, (2013).
Impact/Purpose:
Presents results of field project evaluating problems with current LCR sampling protocol covered in a recent journal paper, and shows possible impact of pipe disturbances during routine infrastructure renewal work and reduction in water use.
Description:
US EPA Region 5 conducted a sampling study that demonstrates existing sampling protocols used for the Lead and Copper Rule (LCR) underestimate peak and probable mass of lead released in a system with lead service lines (LSLs). This comparative stagnation sampling was conducted in 32 single-family homes in Chicago, a system treated with a blended phosphate corrosion inhibitor for the last 19 years. Lead levels were highest within the LSLs, with maximum values 4-6 times higher than the system’s regulatory compliance results. There was significant variability in values within individual LSLs and between different LSL sites. Sites with known documentable disturbances to the LSLs had the highest Pb results, though other factors could additionally be playing a role. This study illustrates the importance of sample site selection, sampling protocol, and other factors, in accurately assessing the level of Pb corrosion in a public water system and the effectiveness of central water treatment in limiting lead release to consumers. Different sampling protocols were used to collect samples for comparison, and information on water mains, water use, LSL disturbances, plumbing materials and site history were provided both by the City and the sampling volunteers. The sampling protocol analysis included: 1) Comparison of results from both first-draw normal household use and first-draw pre-flushed samples; 2) Evaluation of Pb levels throughout the plumbing sequence using sequential one-liter sample results at each site and comparison with first-draw sample results; 3) Evaluation of flushed sample results, after 45 seconds to 7 minutes of flushing, to evaluate the effectiveness of flushing for Pb mitigation; 4) Analysis of the concentrations of copper (Cu), iron (Fe) and zinc (Zn), in addition to Pb, at each site to correlate sampling results with potential Pb sources within the plumbing; 5) Evaluation of measured LSL Length on Pb levels; 6) Relevance of known plumbing disturbances at each site; and 7) Relevance of water usage data for metered sites. The findings provide valuable information for systems with LSLs in determining the actual level of Pb corrosion that is occurring within the plumbing network in order to assess the adequacy of treatment to better protect public health. While some lead profiles have been published from other studies, this study provides a unique look at the results of a long-term blended phosphate treatment program with a comparatively stable background water quality.
